1. Field of the Invention
The present invention relates to an exhaust gas recirculation (EGR) system of an internal combustion engine, and more particularly, to an atmospheric pressure compensation system for adjusting a control vacuum for controlling an EGR valve in response to changes of the atmospheric pressure. The atmospheric pressure compensation system of this invention can be advantageously employed in an EGR system of a diesel-type engine.
2. Description of the Prior Art
Conventional atmospheric pressure compensation systems of vacuum control valves are known in which metal bellows are used for detecting the atmospheric pressure, and ceramic diaphragms are used for confining the absolute vacuum, so that the atmospheric compensation is carried out by utilizing the pressure difference between the absolute vacuum and atmospheric pressure. However, such conventionally known systems have several disadvantages, such as, they require expensive parts, and it is technically difficult to enclose or confine the absolute vacuum pressure, thereby also requiring high technical costs.